Interplay between magnetic properties and thermoelectricity in misfit and Na cobaltates

Abstract

We present a comparative study of CoO2 layers in the Bi-misfit and NaxCoO2 cobaltates. Co NMR measures the intrinsic susceptibility of the Co layers and is not affected by spurious contributions. At low dopings where room-temperature thermopower (TEP) is large, Curie-Weiss susceptibilities are observed in both materials. But NMR and muSR experiments find neither charge nor spin order down to low temperatures in Bi-misfit, in contrast to the case of NaxCoO2. This demonstrates that metallicity, charge and magnetic orders are specific of the Na layers in NaxCoO2 whereas strong correlations are generic of the cobaltates physics and could explain the large TEP.

arXiv comment4 pages

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• Magnetic and transport properties of the spin-state disordered oxide La0.8Sr0.2Co_{1-x}Rh_xO_{3-δ}
• From quantum criticality to enhanced thermopower in strongly correlated layered cobalt oxide
• Spin polaron theory for the photoemission spectra of layered cobaltates
• Interplay of frustration, magnetism, charge ordering, and covalency in a model of Na0.5CoO2
• Magnetic field dependent specific heat and enhanced Wilson ratio in strongly correlated layered cobalt oxide
• Considerable non-local electronic correlations in strongly doped Na${}_x$CoO${}_2$
• Dual electronic states in thermoelectric cobalt oxide
• Ionic Hubbard model on a triangular lattice for Na_0.5CoO_2, Rb_0.5CoO_2 and K_0.5CoO_2: Mean-field slave boson theory
• New electronic orderings observed in cobaltates under the influence of misfit periodicities
• ω/T scaling of the optical conductivity in strongly correlated layered cobalt oxide